HK1048789B - Method for applying coloured characters on a data storage medium which is preferably made from plastic and data storage media according to said method - Google Patents

Description

The invention relates to a process for applying coloured signs to a data carrier preferably made of plastic as defined in the notion of claim 1 and claim 2 and to a data carrier manufactured by this process as defined in claim 3.

Data carriers, preferably made of plastic, are available in a variety of configurations, such as credit cards, access cards, bank cards and the like, and are used in a variety of service areas. For the various applications, the data carriers usually have an integrated circuit, the so-called chip module, on the front and, additionally or alternatively, a magnetic strip on the back of the data carrier. Both the chip module and the magnetic strip contain information of an electronic nature necessary for the use of the carrier in the various service areas. The information on these components can only be read by means of specialised devices.

The methods for the application of such signs to data carriers may be carried out in the following different ways: according to the state of the art, black signs are applied by burning letters, numbers or patterns into the surface of the respective data carriers by means of a laser system. The colour coating is accompanied by carbonation. Colour markings cannot be produced in this way. For colour signs, it is rather necessary to equip the data carriers with several layers of colour, etc., which are then carried in a second step in the process of personalization of the data carriers by a laser system to the depth at which the respective colour layer is arranged within the data carrier.

It is known that certain pigments irreversibly change color when exposed to light. Thus, pigments are known from DE 695 04 238 T2 which change their optical properties, in particular their colour, when irradiated with laser light. However, there is no indication in this patent that latent pigments are used which change colour from almost colourless or faintly coloured to a state of colour by irradiation with laser light in the infrared range and/or visible range.

EP 0 190 997 A2 refers to a film produced using 1,4-dicheto-3,6-di-parachlorphenyl-pyrrolo-[3,4-c]pyrrol pigments. When irradiating this film with an Nd:YAG pulsed laser, a black label with good contrast is produced.

DE 39 08 312 A1 describes diketopyrrolopyrroles which, when crystallized, contain solvents and become highly fluorescent. At higher temperatures the solvent is released again, thereby eliminating fluorescence.

DE 39 01 988 A1 describes a chemical compound which crystallizes from organic solvents in an orange modification and turns yellow upon heating. Since the original colour modification is present, it is not a latent pigment and therefore no colour change from colourless or faintly coloured to coloured is possible.

DE 39 17 294 A1 lists additives which have a high absorption capacity in the IR and/or UV spectral range.While these additives allow labelling by IR and/or UV laser radiation, no latent pigments are used, but only the fact that the additives can be coloured with pigments and/or dyes at will.

JP-A-08 187 939 describes a laminated magnetic stripe card and a method for its manufacture, which consists of several layers. A laser beam in the IR wavelength range is transmitted by the transparent protective layer permeable to the wavelength of the laser beam, permeable to the infrared absorbing layer of such a magnetic stripe card. This infrared absorbing layer contains an infrared absorbing medium which reacts exothermally to the absorption of infrared laser light.

EP-A-0 296 289 describes a diazo imaging material for the production of multicolored images using a variety of infrared rays with different wavelengths. This photosensitive material has a variety of heat-soluble capsules containing the infrared absorbent. After image production, the material is irradiated with UV light to fix the images.

Finally, an organic material is known from EP 0 327 508 A2 which contains, on the one hand, a bleachable additive consisting of at least one azo and/or indanthron pigment and, on the other hand, a non-bleachable compound consisting of at least one inorganic and/or organic pigment and/or a polymer soluble dye. This means that no latent pigment is used but a combination of a bleachable and a non-bleachable pigment. To ensure a contrast between a bleached and an unbleached area, it is necessary for this material to cover the non-bleachable pigment. The user is therefore limited to dark shades to cover the non-bleachable pigment.

The above methods are relatively unsatisfactory in terms of the security of the forgery by subsequent manipulation of the characters, since of course the authorized personalization of the card by, for example, a combination of numbers and letters at any later time with the help of a suitable laser system can be followed by an unauthorized change of this data. Although possibilities have become known to increase the security of the forgery, various security features, such as encodings embedded with infrared light readable inside the data carrier card, holographic storage methods and the like, can be applied to the card.

The purpose of the invention is therefore to provide a method for the application of coloured characters to data media, preferably made of plastic, which is simple and inexpensive and which also provides a previously unknown degree of counterfeit protection against unauthorised manipulation of the information present on a data medium that is visually readable.

This problem is solved by the method of the invention in which latent pigments, introduced into a surface layer or near-surface layer of the data carrier and in which a change in the absorption behaviour of the pigments is caused by energetic stimulation, are energetically stimulated by laser irradiation on the shafts of the data carrier intended for the signs in such a way that a colour change occurs in the pigments and that, after the colour change of the irradiated latent pigments, the pigments not stimulated by laser irradiation are energetically stimulated by a light wave in the UV wavelength range in such a way that a colourlessness of the pigments is induced in the irradiated pigments.

In addition, the problem is solved by first stimulating latent pigments in a surface layer or near-surface layer of the data carrier, whereby the absorption behaviour of the pigments is altered by energetic stimulation, by irradiation with light waves in the UV wavelength range at points not intended for display, in such a way that the previously irradiated pigments are rendered colourless and by second stimulating the latent pigments at points intended for display in the surface layer by laser irradiation in such a way that a colour change occurs in the latent pigment.

Since the latent pigments can be implemented in a data carrier in a cost-effective manner in different ways, a particularly cost-effective manufacturing process for the colour labelling or marking of a data carrier, such as a chip card, can be obtained, which can eliminate the previously common multi-layered, complex construction with different colour layers. The latent pigments are, for example, diketo-pyrrolo-pyrrole, which, as a result of thermal stimulation, can replicate in diketo-pyrrolo-pyrrol system pharmaceuticals. In the unadulterated state, the coloured pigments are either colourless or weakly colourless.If a colour change has occurred as a result of laser light irradiation, this process is irreversible, i.e. subsequent alteration of the pigments by further irradiation is no longer possible. In addition, with regard to the safety of the picking, it should be noted that the latent pigments may be arranged inside the data carriers, provided that irradiation by transparent protective layers above them is possible.

To increase the resistance to forgery of coloured signs produced by the first process step of the invention on a data carrier, the laser irradiation of a data carrier is connected to the second downstream process step.

The second step of the process described takes advantage of the property of latent pigments that different energetic stimulation can produce a different colour change of the latent pigments. Thus, if after the application of the coloured signs, letters or other patterns of the data carriers are irradiated with UV light on a large area, the latent pigments not yet energetically affected are transformed into their colourless state. This conversion is of course as irreversible as the addition of coloured signs by means of a laser beam described above.

It is also conceivable, of course, to perform the steps described in reverse order: in the first step, the latent pigments placed in a surface layer of the data carriers are energized at the points not intended for display by irradiation with light waves in the UV wavelength range, so that the irradiated pigments are rendered colourless.

The invention also relates to a data carrier with a carrier body, produced by the method described above, in which latent pigments are arranged in at least one sublayer of the carrier body in such a way that irradiation by a laser system and UV irradiation cause an energetic excitation of the latent pigments to solve the problem.

The latent pigments may be arranged in different ways in or on the carrier body according to the characteristics of subclauses 4 to 8.

For example, it is possible to arrange the latent pigments in a cover film applied to the outer surface of the data carrier, which is an advantageous design, and which can be produced in a simple and inexpensive way and connected to the carrier body in an equally cost-effective manner.

In addition, it is conceivable to incorporate the latent pigments into a coating system, whereby the coating system may, for example, provide for a lacquer or adhesive agent during the production of the data carrier, which is usually done by screen, offset, stamping or rolling, although of course a full or partial coating is conceivable, so that only certain areas of the data carrier surface can be provided for color marking carried out according to the method of the invention.

The latent pigments may also be arranged in an overlay layer and/or in a near-surface layer covered by the overlay layer.

An alternative method of incorporating the latent pigments into a data carrier is to enrich the material of the carrier with the latent pigments before the molding process for the carrier body, for example by injection molding, which may enrich the entire card body with the latent pigments or may use the multi-component injection molding technique to produce certain parts of the carrier body from the material enriched with the latent pigments.

All the above methods of storage represent a simple and cost-effective way of implementing the latent pigments necessary for the storage of coloured characters on storage media in or on the storage media.

The term 'signs' includes not only letters, numbers, special characters, logos, etc., but also patterns, pictures or photographs.

The following illustrations of the data carriers of the invention are further explained by means of interfaces of the body of the data carriers.

It shows: Figure 1 a cross-section of a multi-layered carrier body in the compound process and Figure 2 a cross-section of an injection-moulded carrier body and Figure 3 a schematic diagram of the absorption behaviour of a latent pigment depending on the wavelength of the light that is irradiated.Figure 4 a structural formula for an example of a latent pigment: N,N'-bis-iso-pentoxycarbonyl-1,4-diketo-3,6-di-chlorophenyl) pprolo[3,4-c]pyrrolFigure 5 a structural formula for an example of a pigment: 1,4-diketo-3,6-di-chlorophenylpyrrol[3,4-pyrrol]

The chip card-shaped data carrier body shown in Figure 1 consists essentially of two core films 1 and 2, on which transparent cover films 3, 4, 5 and 6 are applied on the top and bottom of the data carrier. In the example shown, between cover films 5 and 6 there is a coating layer 7, consisting of an adhesive or lacquer in which the latent pigments are implemented. The lacquer or adhesive layer 7 is thus protected under the immediate surface of the data carrier, but can be energized by laser irradiation from the transparent cover film 6, so that an energetic stimulation of the latent pigments is possible, which causes a pigment coating to be applied to the affected areas.

Alternatively to the laser beam source, another high-energy, highly concentrated light source emitting light in the visible or IR range may be used, where necessary using optical filters to eliminate the interfering wavelengths.

Lamps or UV lasers can be used as light sources for UV radiation, and if necessary, the interfering wavelengths of these light sources are filtered out by optical filters.

On the opposite side of the surface of the data carrier, a coating layer 8 is placed between the deck films 3 and 4 in the same way as described above, and between the deck film 4 and the core film 1 there is another coating layer 9 so that different latent pigments can be implemented in the coating layers 8 and 9 in order to produce different coloured signs.

Alternatively, the latent pigments may also be contained in at least one deck film 3, 4, 5, 6.

It is also possible, of course, to introduce latent pigments into the material of core films 1, 2 or cover films 3, 4, 5, 6 and then to compress them into a data carrier body.

The data carrier body shown in Figure 2 is a chip card made by injection moulding. The chip card body consists essentially of a core layer 11 with layers of film arranged on both sides of the carrier body. The data carrier body of this design variant is made by the so-called 2K injection moulding process and has a second core layer enriched with latent pigments.

Figure 2 also shows a possibility of labelling or stamping foils 16, 17 on the carrier body, which are then coated with latent pigments in a prefabricated process and placed on or in the carrier.

Of course, it is also conceivable to apply layers of lacquer or adhesive to a carrier body produced by injection moulding, as shown in Figure 2, enriched with latent pigments, in order to introduce the latent pigments into the carrier, which enables them to be marked in colour.

Figure 3 shows how the absorption behaviour of a latent pigment is altered by irradiation with light of different wavelengths (in this case, light with laser wavelength ΔE1 and light in the UV wavelength range ΔE2).

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The following is an example of a possible embodiment of the invention. The chemical compound described in Figure 4 is suitable as a potential latent pigment. Laser irradiation of this compound results in the coloured chemical compound shown in Figure 5. The latent pigment described in Figure 4 is characterized by a faint yellow colouration. At a temperature of about 260 °C, this latent pigment is decomposed and the pigment described in Figure 5 is produced, which is characterized by a brilliant red colouration, Color Index: P.R.254. The data carrier in this example is a plastic card with core foil 1, 2 of polycarbonate, containing a polyurethane-based printing ink with a 5% dilution of a latent pigment in a coating layer 7.The coating layer 7 of the silk-based printing coating mixed with latent pigments is 10 μm thick. This layer is covered with a transparent cover film 6. The laser beam source that triggers the conversion of the latent pigment into the red pigment is a tunable pulsed OPO laser, which in this example emits radiation with a wavelength of 430 nm. The pulse energy of the laser radiation is 60 mJ and the pulse frequency is 1 kHz. The laser beam passes through a lens system that focuses the beam. The diameter of the laser beam is 100 μm in the focus.The laser beam is moved at a right angle at a speed of 10 cm/s to the layer 7 of the carrier body. The area of the layer 7 which was exposed to the laser radiation has taken on a clearly visible red colour. The unradiated area at this time still has the faint yellow colouration of the latent pigment. The surface layer 6 of the carrier body, shown in Figure 1 below, is now irradiated with the light of a xenon arc lamp with a minimum of 0.35 W/m2. The xenon arc lamp emits light with a wavelength of 340 nm. This UV radiation penetrates the transparent cover film 6 and produces a significant bleaching of the pigment layer in the layer 7 of the carrier body.This is expressed by the loss of the faint yellow background color of the disk body.

List of reference marks

1 core film2 core film3 cover film4 cover film5 cover film6 cover film7 coating layer8 coating layer9 coating layer11 core layer12 core layer13 cover layer14 cover layer15 cover layer16 label17 question film

Claims (10)

1. Method for applying coloured marks to a data carrier, preferably made of plastic, by means of a laser system, characterized in that latent pigments which are introduced into at least one surface layer and/or surface-adjacent layer of the data carrier, the absorption characteristics of which pigments are caused to change by energetic excitation, are energetically excited at the areas intended for the marks on the surface of the data carrier by means of laser radiation in the IR and/or visible region in such a way that a colour change occurs in said pigments, and in that, following the colour change of the laser-irradiated latent pigments, the latent pigments not excited by laser radiation are energetically excited by light waves in the UV wavelength region in such a way that the pigments thus irradiated are rendered colourless.
2. Method for applying coloured marks to a data carrier, preferably made of plastic, by means of a laser system, characterized in that in a first method step latent pigments which are introduced into a surface layer of the data carrier, the absorption characteristics of which pigments are caused to change by energetic excitation, are energetically excited at the areas not intended for representing the marks by irradiation with light waves in the UV wavelength region in such a way that the pigments thus irradiated are rendered colourless, and in that in a second method step the latent pigments disposed at the areas intended for representing the marks on the surface layer are energetically excited by means of laser radiation in the IR and/or visible region in such a way that a colour change occurs in said pigments.
3. Data carrier composed of a plastic material with pigments of at least one coloured marking in the form of marks and/or images, characterized in that latent pigments are provided, wherein a change in the absorption characteristics of the pigments is caused by energetic excitation so that in at least one sublayer of the body of the data carrier on the one hand in the case of laser irradiation in the visible and/or IR region a change in colour of the latent pigments irradiated by the laser light occurs, and on the other hand in the case of irradiation with UV light the latent pigments irradiated with UV light are rendered colourless.
4. Data carrier according to claim 3, characterized in that the latent pigments are disposed on a covering film applied to the outer surface of the data carrier.
5. Data carrier according to claim 3, characterized in that the latent pigments are disposed in a core layer which is arranged within the data carrier and is covered by a transparent covering layer to the outside.
6. Data carrier according to claim 3, characterized in that the material of the data carrier is enriched with the latent pigments prior to the forming process for the data carrier:
7. Data carrier according to claim 3, characterized in that the sublayer of the data carrier is a coating applied thereto by means of a pressure technique.
8. Data carrier according to claim 3, characterized in that the sublayer of the data carrier is an adhesion promoter applied thereto by means of a pressure technique.
9. Data carrier according to one of claims 3 to 8, characterized in that the latent pigments belong to the substance group of diketopyrrolopyrroles.
10. Data carrier according to one of claims 3 to 9, characterized in that the UV light source is a UV lamp or a UV laser system.